Relatively highly integrated semiconductor devices and/or relatively complex value-added devices may require processes for determining characteristics of the devices. For example, a pad opening process at final stages of wafer processing may be important. A pad may be connected to a wire during wire bonding in an assembly process for forming a semiconductor chip. The semiconductor device may transmit and/or receive signals through the pad. A pad opening process may be important because a product may not be commercially viable and have to be discarded due to foreign substances on the pad or visual defects, regardless of the device characteristics.
FIGS. 1A to 1D are sectional views illustrating a method of opening a pad in a semiconductor device. As illustrated in FIG. 1A, a pad 12 made of a metal film may formed on and/or over a semiconductor substrate 10. As illustrated in FIG. 1B, a protective film 14 may be formed on and/or over substrate 10 and/or pad 12. Protective film 14 may include silicon nitride (SiN). As illustrated in FIG. 1C, a photosensitive film (e.g. a photoresist) may be used as a mask material to form an opening in pad 12. A photosensitive film may be coated on and/or over protective film 14 and patterned by exposure and development methods to form pad opening pattern 16. Accordingly, a pad opening pattern 16 is formed to partially expose protective film 14. As illustrated in FIG. 1D, exposed protective film 14 may be etched using the pad opening pattern 16 as a mask to open pad 12. Pad opening pattern 16 may then be removed.
An example of a visual defect that may remain on the pad of the semiconductor device is pit-like pad corrosion 18 illustrated in FIG. 1D. Such a pad corrosion 18 may adversely affect qualitative characteristics of a packaging process. At least for this reason, it may be necessary and/or desirable to manage and/or limit the degree of pad corrosion to a predetermined limit. There are different reasons for pad corrosion. For example, when etching protective film 14 on pad 12, CxFy-based gas may be used. Then, an organic polymer containing C and F groups may consequently remain on the surface of the pad 12 and reacts with moisture (H2O) in a subsequent process. This reaction may cause corrosion 18. Further, C and F groups may exist during dry etching. Similarly, C and F groups may react with moisture in a subsequent process and this reaction may cause corrosion 18. If pad corrosion occurs, resistance may become relatively high. Relatively high resistance may cause deterioration of the characteristics of the semiconductor device.